A waveguide is any structure which permits the propagation of a wave through its length despite diffractive effects, and possible curvature of the guide structure. An optical waveguide is an optical structure capable of guiding a beam of laser light along light channels in the waveguide, and is defined by an extended region of increased index of refraction relative to the surrounding medium. The waveguide typically includes both the light channels in which light waves propagate in the waveguide, and surrounding cladding which confine the waves in the channel. The strength of the guiding, or the confinement, of the wave depends on the wavelength of light, the refractive index difference between the guide and the cladding, and the guide dimensions.
Discrete control of the refractive index of a given functional optical material is necessary for creating silica or non-silica waveguide optical switch components; however, it is not the only property, which determines the durability and efficiency required for a commercial product. The present invention demonstrates that there is a critical interplay between the polymer, the substrate, the electrodes and the electro-optic material which must be elucidated to create a commercially viable product.
Bosc et al., describe the use of two fluorinated monomers (1H, 1H, 2H, 2H tridecafluoro-octyl methacrylate and trifluoroethyl methacrylate) to create passive copolymers having refractive index values between 1.370 and 1.403 at 1.3 um (Design and Synthesis of Low Refractive Index Polymers for Modulation in Optical Waveguides, Optical Materials Vol. 13 (1999), pp. 205-209). Bosc, et al. further discuss copolymerization of an electro-optic monomer, methacrylic acid ester of Disperse Red 1 (the refractive index for a homopolymer of this material is 1.710). These monomers were blended to achieve a final terpolymer refractive index greater than 1.5. The Tg of these systems varied between 82° C. and 92° C. While these compositions allow (possess) some degree of optical modulation, they are not suitable for use in an optical switch, which requires the reliability and efficiency requirements of commercial communications networks.